EP1637015A1 - Modulation de la puissance lumineuse pour la transmission de donnees - Google Patents

Modulation de la puissance lumineuse pour la transmission de donnees

Info

Publication number
EP1637015A1
EP1637015A1 EP04735929A EP04735929A EP1637015A1 EP 1637015 A1 EP1637015 A1 EP 1637015A1 EP 04735929 A EP04735929 A EP 04735929A EP 04735929 A EP04735929 A EP 04735929A EP 1637015 A1 EP1637015 A1 EP 1637015A1
Authority
EP
European Patent Office
Prior art keywords
drive signal
pulse width
width modulated
data period
waveform
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP04735929A
Other languages
German (de)
English (en)
Other versions
EP1637015B1 (fr
Inventor
Xiaohong Sun
Demetri J. Giannopoulos
Laurence Bourdillon
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Koninklijke Philips NV
Original Assignee
Koninklijke Philips Electronics NV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Koninklijke Philips Electronics NV filed Critical Koninklijke Philips Electronics NV
Publication of EP1637015A1 publication Critical patent/EP1637015A1/fr
Application granted granted Critical
Publication of EP1637015B1 publication Critical patent/EP1637015B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/26—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc
    • H05B41/28—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters
    • H05B41/282—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters with semiconductor devices
    • H05B41/2825—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters with semiconductor devices by means of a bridge converter in the final stage
    • H05B41/2828—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters with semiconductor devices by means of a bridge converter in the final stage using control circuits for the switching elements
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/36—Controlling
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/36—Controlling
    • H05B41/38—Controlling the intensity of light
    • H05B41/39—Controlling the intensity of light continuously
    • H05B41/392—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor
    • H05B41/3921—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations
    • H05B41/3927—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations by pulse width modulation

Definitions

  • the invention relates to light source data transmission. More specifically, the invention relates to a method and system for transmitting data utilizing a fluorescent light source and light output modulation.
  • AM analog amplitude modulation
  • FM frequency modulation
  • frequencies above the audible range include at least two frequency ranges that should not be utilized.
  • One frequency range example is the RC-5 frequency range (30 - 42 kHz), utilized for infrared remote control. Lamps operating in this frequency range can interfere with the operation of the RC-5 remote control receivers.
  • Another frequency range example is the anti-theft protection gate frequency range (56 - 60 kHz), utilized in U.S. retail establishments.
  • the EM field generated by the ballast of the fluorescent lamp can disturb the proper operation of the anti-theft protection gates. Since the frequency range of the ballast operation is continuous, the ballast should operate either above or below these frequency ranges.
  • ballast lamp stability characteristics are a complex function of the relative values of the ballast output impedance and the lamp impedance.
  • the ballast output impedance will vary with frequency and the lamp impedance will vary non-linearly with power dissipation. For this reason, with a fixed- ballast design, full dimming using frequency variation is generally achieved only for a limited number of lamp types. For other lamp-ballast combinations, dimming will not be possible over the entire range and therefore not commercially viable.
  • Pulse-width modulation (PWM) based control methods have been utilized to address the frequency range problems.
  • Pulse-width modulation (PWM) based control methods which use a fixed frequency of operation, offer advantages and can be applied in multi-lamp type ballasts.
  • PWM based control methods are implemented using either a digital ballast or an analog ballast. Therefore, PWM can be implemented utilizing a fixed frequency outside the undesirable frequency ranges.
  • One form of the invention is a method operating a light source including a ballast in electrical communication with a lamp.
  • the ballast determines an average lamp power to be applied to the lamp during a data period, and communicates a generated pulse width modulated drive signal to the lamp during the data period.
  • the pulse width modulated drive signal has either one of a first waveform or a second waveform for applying the average lamp power to the lamp during the data period.
  • the first waveform includes one or more pulses representative of a first data bit
  • the second waveform includes one or more pulses representative of a second data bit.
  • the lamp emits a modulated light output during the data period in response to receiving the pulse width modulated driver signal.
  • the modulated light output is either representative of the first data bit in response to the pulse width modulated drive signal having the first waveform or representative of the second data bit in response to the pulse width modulated drive signal having the second waveform.
  • Another form of the invention is an apparatus including a lamp and a ballast in electrical communication with the lamp.
  • the ballast is operable to determine an average lamp power to be applied to the lamp during a first data period.
  • the ballast is further operable to generate and communicate a pulse width modulated (PWM) drive signal to the lamp during the data period.
  • the PWM drive signal includes either a first waveform or a second waveform for applying the average lamp power to the lamp.
  • the first waveform includes one or more pulses representative of a first data bit
  • the second waveform includes one or more pulses representative of a second data bit.
  • the lamp is operable to emit a modulated light output responsive to a reception of the PWM drive signal during the data period.
  • the modulated light output is representative of the first data bit in response to the PWM drive signal having the first waveform
  • the modulated light output is representative of the second data bit in response to the PWM drive signal having the second waveform.
  • FIG. 1 is a schematic diagram illustrating a programmable digital ballast, within a light source, in accordance with one embodiment of the present invention
  • FIG. 2 is a graph illustrating a transfer curve defining the relationship of lamp power versus duty cycle for the lamp portion of the digital ballast in FIG. 1 ;
  • FIG. 3 is a waveform diagram illustrating a symmetric bi-phase pulse width modulated waveform, expressing a "0" bit, as may be applied in an embodiment of the invention
  • FIG. 4 is a waveform diagram illustrating a symmetric bi-phase pulse width modulated waveform, expressing a "1" bit, as may be applied in an embodiment of the invention
  • FIG. 5 is a waveform diagram illustrating an asymmetric pulse width modulated waveform, expressing a "0" bit, delivering a greater average lamp power in an embodiment of the invention
  • FIG. 6 is a waveform diagram illustrating an asymmetric pulse width modulated waveform, expressing a "1" bit, delivering a greater average lamp power in an embodiment of the invention
  • FIG. 7 is a waveform diagram illustrating an asymmetric pulse width modulated waveform, expressing a "0" bit, delivering a lesser average lamp power in an embodiment of the invention
  • FIG. 8 is a waveform diagram illustrating an asymmetric pulse width modulated waveform, expressing a "1" bit, delivering a lesser average lamp power in an embodiment of the invention
  • FIG. 9 is a flow diagram depicting a method of modulating a light output for data transmission in accordance with the present invention.
  • FIG. 1 is a schematic diagram illustrating a programmable digital ballast within a light source 100 in accordance with one embodiment of the present invention.
  • Light source 100 transmits data via light output modulation.
  • Light source 100 includes programmable digital ballast 110 and lamp 120.
  • Light source 100 includes a communication transceiver interface imbedded (not shown) within programmable digital ballast 110 for receiving data for transmission as well as control functions.
  • programmable digital ballast 110 includes a microprocessor 130, level shifter 140, resonance tank 150, transistors (Mi and M 2 ), and capacitor C dc - Programmable digital ballast 110 is arranged in a half-bridge driver configuration and produces a non- overlapping driving signal based on the configuration.
  • Microprocessor 130 includes a data signal input terminal (Data), a control signal input/output terminal CTL, a first output signal terminal G ls and a second output signal terminal G 2 .
  • Data data signal input terminal
  • control signal input terminal CTL control signal input terminal
  • Level shifter 140 includes a first input signal terminal G ⁇ and a first output signal shifted terminal G ⁇ + .
  • the first input signal terminal Gi of level shifter 140 is coupled to first output signal terminal Gj . of microprocessor 130.
  • Transistors Mj and M 2 are field effect transistors (FETs), each having a source, a gate, and a drain.
  • the source of transistor M ⁇ is coupled to a voltage source V + and the gate of transistor M ⁇ is coupled to the first output signal shifted terminal G ⁇ + .
  • the source of transistor M 2 is coupled to the drain of transistor Mi.
  • the gate of transistor M 2 is coupled to second output signal terminal G 2 and the drain of transistor M 2 is coupled to a circuit ground GND.
  • Capacitor C c includes a first terminal and a second terminal. The first terminal of capacitor C dc is coupled to the drain of transistor Mi and the source of transistor M 2 .
  • Resonance tank 150 includes an inductor L R and a capacitor CR.
  • Inductor L R of resonance tank 150 includes a first terminal and a second terminal. The first terminal of inductor L R is coupled to the second terminal of capacitor C dC .
  • Capacitor C R of resonance tank 150 includes a first terminal and a second terminal. The first terminal of capacitor CR is coupled to the second terminal of inductor L R .
  • the second terminal of capacitor C R is coupled to a circuit ground GND.
  • Lamp 120 includes a first terminal and a second terminal.
  • the first terminal of lamp 120 is coupled to the second terminal of inductor L R and the first terminal of capacitor C R .
  • the second terminal of lamp 120 is coupled to ground GND.
  • microprocessor 130 receives a control signal at the control signal input terminal CTL and an input data signal at the data signal input terminal Data.
  • the control signal includes a light source output level instruction.
  • the light source output level instruction is a user determined light source output level instruction based on a user determined light output level.
  • the input data signal includes input data in the form of communication data or fixed code for maintaining the user determined light output level.
  • Microprocessor 130 produces gate drive signals based on the received control signal and input data signal.
  • the control signal is utilized to determine a duty cycle (detailed in FIG. 2, below). Methodology for producing the aforementioned duty cycle is well known in the art.
  • the determined duty cycle and the input data signal are utilized to produce two pulse width modulated gate drive signals that result in turn a pulse width modulated tank drive signal as described below.
  • the gate drive signals are bi-phase signals (detailed in FIG. 2, below). Bi-phase signals eliminate flickering.
  • the gate drive signals are generated utilizing pulse width modulation without bi-phase coding.
  • a first gate drive signal is transmitted from first output signal terminal Gi of microprocessor 130 to first input signal terminal G ⁇ of level shifter 140.
  • Level shifter 140 shifts the first gate drive signal and produces a shifted first gate drive signal at first output signal shifted terminal G ⁇ + .
  • the shifted first gate drive signal is transmitted from first output signal shifted terminal G ⁇ + to the gate of transistor M 2 .
  • the first gate drive signal is shifted by increasing the signal so that the shifted first gate drive signal will be large enough to affect the gate of transistor Mi . relative to the voltage applied to the source of transistor Mi . by voltage source V + .
  • a second gate drive signal is transmitted from second output signal terminal G 2 of microprocessor 130 to the gate of transistor M 2 .
  • the shifted first gate drive signal and the second gate drive signal drive the associated transistors (M ⁇ and M 2 ) and produce the pulse width modulated signal drive signal at the first terminal of capacitor C dc - Capacitor Cdc filters and removes low frequency (direct current) portions of the pulse width modulated signal drive signal.
  • the filtered pulse width modulated drive signal is then applied to resonance tank 150.
  • increasing the duty cycle of the driving signal will increase the power transferred to the lamp, thus increasing the lamp light output.
  • Resonance tank 150 is a frequency dependant circuit.
  • the impedance of both the inductor L R and capacitor C R change as the frequency of the pulse width modulated drive signal changes.
  • resonance tank 150 receives the pulse width modulated tank drive signal and delivers a power signal to the lamp based on the pulse width modulated tank drive signal. For example, at a high frequency, the impedance of resonance tank 150 is large and therefore the power delivered to lamp 120 is low. Conversely, at a low frequency, the impedance of resonance tank 150 is low and therefore the power delivered to lamp 120 is high.
  • the power delivered to lamp 120 causes the intensity of the lamp to change at a very- high rate for varying lengths of time. This rate is referred to as the switching frequency of the half bridge within the digital ballast. If the switching frequency is maintained at a high enough rate, it will not be visible to the human eye. In one embodiment, a switching frequency of greater than 30 kilohertz is utilized and will insure that visible flickering does not occur.
  • Light source 100 can be implemented as any suitable fluorescent light source including a programmable digital ballast, such as, for example the fluorescent light source including programmable digital ballast described in Circuit Arrangement as disclosed by Beij, Buij, Aendekerk, and Langeslag in WO 02/35893 published on May 2, 2002 and US2002/0093838 Al published on July 18, 2002.
  • a programmable digital ballast such as, for example the fluorescent light source including programmable digital ballast described in Circuit Arrangement as disclosed by Beij, Buij, Aendekerk, and Langeslag in WO 02/35893 published on May 2, 2002 and US2002/0093838 Al published on July 18, 2002.
  • light source 100 receives a control signal that is based on a desired lamp/light output level.
  • Microprocessor 130 of programmable digital ballast 110 determines an average lamp power to be applied to lamp 120 that is required to produce the desired average lamp/light output level.
  • Programmable digital ballast 110 generates and communicates a pulse-width modulated (PWM) drive signal to lamp 120 based on the average lamp power determination. Generation of the PWM drive signal is described in FIGS. 2 - 8, below.
  • Lamp 120 emits a modulated light output responsive to reception of the generated PWM drive signal.
  • FIG. 2 is a graph, including an x-axis and a y-axis, illustrating a transfer curve defining the relationship of average lamp power versus duty cycle for the lamp portion of the digital ballast in FIG. 1.
  • the transfer curve represents characteristics of a dimmable ballast that is utilized to drive a fluorescent lamp.
  • the transfer curve represents characteristics of digital ballast 110 of FIG. 1.
  • average lamp power is illustrated as the y-axis and duty cycle is illustrated as the x-axis.
  • duty cycle is an expression of a percentage of time a lamp is producing light as compared to the amount of time within a predetermined period.
  • P max and P m i n represent the maximum and minimum rated power outputs of a fluorescent lamp.
  • d max and d m i n represent the corresponding maximum and minimum duty cycles to achieve the respective average power levels. Because lamp power levels in a biphase PWM driving scheme are averages, the levels of maximum rated power output P ma ⁇ and minimum rated power outputs P m i n would be exceeded during a transmission by the peak- to-peak levels of the pulse width modulated drive signal. Therefore, a percentage of each level of maximum rated power output P max and minimum rated power outputs Pmin is identified as the maximum and minimum delivered average power level for the lamp associated with the transfer curve.
  • the maximum and minimum delivered average power levels are identified as P h and Pi respectively. Determining factors for P h and Pi include dimming range of the lamp and signal to noise ratio of the data transmission. In an example, maximum delivered average power level P h is ninety percent (90%) of the value of maximum rated power output P max , and minimum delivered average power level Pi is twenty percent (10%) of the value of maximum rated power output P ma ⁇ . Each average power level has a corresponding duty cycle associated with it, dh and di respectively.. In one embodiment and referring to FIG. 1, transfer curve data for one or more fluorescent lamps is stored in a look-up table within microprocessor 130.
  • values for maximum delivered average power level Ph and minimum delivered average power level Pi representing the maximum and minimum delivered average power outputs of each fluorescent lamp model are stored within microprocessor 130 as well.
  • P m represents an average lamp power level associated with a lamp.
  • the average lamp power level P m is a user defined level of luminance.
  • d m represents a corresponding average duty cycle associated with the average lamp power level P m .
  • the average duty cycle d m is determined by the feedback regulation loop in the lamp driver to set the average lamp power level P m to the level selected by the user.
  • ⁇ dj and ⁇ d n are design variables that are added to or subtracted from the average duty cycle d m to facilitate the detection of the light modulation by an optical receiver.
  • Moving maximum delivered average power level P h and minimum delivered average power level Pi away from maximum rated power output P ma ⁇ and minimum rated power output P m i n requires a corresponding movement of maximum average duty cycle d and minimum average duty cycle di away from maximum duty cycle d ma ⁇ and minimum duty cycle d m in- Moving maximum average duty cycle d h and minimum average duty cycle di away from maximum duty cycle d ma ⁇ and minimum duty cycle d m i n results in a reduction of area for the range of the average duty cycle plus the design variable (d m + ⁇ di) and the average duty cycle plus the design variable (d m + ⁇ d n ) to occupy.
  • design variables ( ⁇ di and ⁇ dh) are provided by the software and stored within microprocessor 130, such as, for example in a look-up table.
  • design variables ( ⁇ di and ⁇ d h ) are provided by a lamp manufacturer and up- linked to microprocessor 130 for use when the lamp is installed.
  • an average lamp output P m associated with the light/lamp output level and a corresponding average duty cycle d m are determined.
  • design variables ( ⁇ di and ⁇ d h ) are added to and subtracted from the average duty cycle d m to determine a duty cycle range [(d m + ⁇ di) to (d m + ⁇ d h )].
  • a symmetric bi-phase driving signal is produced. Such a symmetric bi-phase driving signal is illustrated in FIGS. 3 and 4, below.
  • an asymmetric bi-phase driving signal delivering a greater than average lamp power is produced.
  • Such an asymmetric pulse width modulated driving signal is illustrated in FIGS. 5 and 6, below.
  • an asymmetric bi-phase driving signal delivering a less than average lamp power is produced.
  • Such an asymmetric pulse width modulated driving signal is illustrated in FIGS. 7 and 8, below.
  • FIGS. 3 and 4 are waveform diagrams illustrating symmetric bi-phase pulse width modulated waveforms as may be applied in an embodiment of the invention.
  • the use of a symmetric pulse width modulated driving signal waveform is referred to as a symmetric coding scheme.
  • the symmetric coding scheme is defined by the utilization of one-half of a data period T d ta for each half "bit" portion of the waveform.
  • a "0" bit is expressed by the first half of the data period T d at including wide pulses, and the second half of the data period T dat including narrow pulses.
  • a "1" bit is expressed by the first half of the data period Tdat including narrow pulses, and the second half of the data period T data including wide pulses.
  • the symmetric coding scheme could be employed in a reverse implementation.
  • the duty cycle of the wide pulses is determined by the design variable ⁇ d h .
  • the duty cycle of the wide pulses is equal to the value of the sum of the average duty cycle d m and the design variable ⁇ d h , expressed (d m + ⁇ d h ), where ⁇ d h is positive.
  • the duty cycle of the narrow pulses is defined by the design variable ⁇ di. That is, the duty cycle of the narrow pulses is equal to the value of the sum of the average duty cycle d m and the design variable ⁇ di, expressed as (d m + ⁇ di), where ⁇ di is negative.
  • FIGS. 5 and 6 are waveform diagrams illustrating asymmetric bi-phase pulse width modulated waveforms as may be applied in an embodiment of the invention.
  • the use of an asymmetric bi-phase driving signal waveform is referred to as an asymmetric coding scheme.
  • the asymmetric coding scheme is defined by the utilization of greater than one-half of a data period T ata for one "bit" portion of the waveform, and utilization of less than one- half of a data period T d ta for another "bit" portion of the waveform.
  • a "0" bit is expressed by the first portion of the data period T data including wide pulses, and the second portion of the data period Tdata including narrow pulses.
  • a "1" bit is expressed by the first portion of the data period T data including narrow pulses, and the second portion of the data period T a t a including wide pulses.
  • the "0" bit is expressed by the first portion of the data period T data utilizing two-thirds ( 2 ) of the data period T dat a- Therefore, the utilized two-thirds (%) of the data period T ata would include wide pulses and the remaining one-third (V_) of the data period T data would include narrow pulses.
  • the "1" bit is expressed by the first portion of the data period T d ata utilizing one-third (V3) of the data period Tda ta - Therefore, the utilized two-thirds (%) of the data period Tdat would include wide pulses and the remaining one-third (V3) of the data period Tda t a would include narrow pulses.
  • the duty cycle of the wide pulses is determined by the design variable ⁇ d h . That is, the duty cycle of the wide pulses is equal to the value of the sum of the average duty cycle d m and the design variable ⁇ dh, expressed as (d m + ⁇ d h ), where ⁇ d h is positive.
  • the duty cycle of the narrow pulses is determined by the design variable ⁇ di. That is, the duty cycle of the narrow pulses is equal to the value of the sum of the average duty cycle d m and the design variable ⁇ di, expressed as (d m + ⁇ di), where ⁇ di is negative.
  • the asymmetric coding scheme utilized in FIG 5 and 6 results in an increase in average lamp power.
  • the increase in average lamp power allows the sum of the average duty cycle d m and the design variable ⁇ d h , expressed as (d m + ⁇ d h ) to operate closer to maximum duty cycle d ma ⁇ -
  • the result of the sum of the average duty cycle d m and the design variable ⁇ d h , expressed as (d m + ⁇ d h ) operating closer to the maximum duty cycle d max is the movement of the maximum average duty cycle d h closer to the maximum duty cycle d max -
  • This asymmetric coding scheme allows for a wider range of operation for the lamp and hence the light source.
  • FIGS. 7 and 8 are waveform diagrams illustrating asymmetric bi-phase pulse width modulated waveforms as may be applied in an embodiment of the invention.
  • the use of an asymmetric bi-phase driving signal waveform is referred to as an asymmetric coding scheme.
  • the asymmetric coding scheme is defined by the utilization of greater than one-half of a data period T data for one "bit" portion of the waveform, and utilization of less than one- half of a data period Td ata for another "bit” portion of the waveform.
  • a "0" bit is expressed by the first portion of the data period T data including narrow pulses, and the second portion of the data period Tdat a including wide pulses.
  • a "1" bit is expressed by the first portion of the data period T da ta including wide pulses, and the second portion of the data period T dat a including narrow pulses.
  • the "0" bit is expressed by the first portion of the data period T data utilizing two-thirds (%) of the data period T da t a - Therefore, the utilized two-thirds (%) of the data period T data would include narrow pulses and the remaining one- third ⁇ ) of the data period T data would include wide pulses.
  • the "1" bit is expressed by the first portion of the data period T d ata also utilizing one- third ( l ⁇ ) of the data period T data . Therefore, the utilized two-thirds (%) of the data period T dat a would include narrow pulses and the remaining one-third ⁇ ) of the data period Tdata would include wide pulses.
  • the duty cycle of the wide pulses is determined by the design variable ⁇ d h . That is, the duty cycle of the wide pulses is equal to the value of the sum of the average duty cycle d m and the design variable ⁇ dh, expressed as (d m + ⁇ d h ).
  • the duty cycle of the narrow pulses is determined by the design variable ⁇ di. That is, the duty cycle of the narrow pulses is equal to the value of the sum of the average duty cycle d m and the design variable ⁇ di, expressed as (d m + ⁇ di)
  • the asymmetric coding scheme utilized in FIGS. 7 and 8 results in a decrease in average lamp power.
  • the decrease in average lamp power allows the sum of the average duty cycle d m and the design variable ⁇ di, expressed as (d m + ⁇ di) to operate closer to the minimum duty cycle d m i n .
  • the result of the sum of the average duty cycle d m and the design variable ⁇ di, expressed as (d m + ⁇ di) operating closer to the minimum duty cycle d m in is the movement of the minimum average duty cycle di closer to the minimum duty cycle d m in-
  • This asymmetric coding scheme also allows for a wider range of operation for the lamp and hence the light source.
  • the asymmetric coding scheme discussed in FIGS. 5 - 8, requires multiple pulses for implementation. A single pulse implementation will result in symmetric coding scheme utilization.
  • asymmetric coding scheme (detail in FIGS. 3 and 4, above) is utilized if the average duty cycle d m , based on the average lamp power level P m , is located between the maximum average duty cycle d h and minimum average duty cycle d ⁇ on the duty cycle range.
  • FIG. 9 is a flow diagram illustrating a method 900 for transmitting a data bit through a fluorescent light source during a single data period.
  • Method 900 may utilize one or more concepts detailed in FIGS. 1 - 8, above.
  • Method 900 begins at stage 910.
  • ballast 110 determines an average lamp power for application during the data period.
  • a desired lamp/light output level is received by ballast 110, and the average lamp power is determined based on the received lamp/light output level.
  • microprocessor 130 of programmable digital ballast 110 includes computer code for determining the average lamp power to be applied to lamp 120 that is required to produce the desired average lamp/light output level during the data period in accordance the transfer curve illustrated in FIG. 2.
  • ballast 110 During stage 920, ballast 110 generates and communicates a pulse-width modulated (PWM) drive signal to lamp 120 during the data period. Based on either input data or a fixed code, the pulse width modulated drive signal includes either a "0" bit waveform or a "1" bit waveform for applying the average lamp power to the lamp 120 during the data period.
  • microprocessor 130 of programmable digital ballast 110 includes computer code for generating the "0" bit waveform to include one or more pulses, such as, for example, the "0" bit waveforms illustrated in FIGS. 3, 5 and 7, and for generating the "1" bit waveform to include one or more pulses, such as, for example, the "1" bit waveforms illustrated in FIGS. 4, 5 and 8.
  • lamp 120 emits a modulated light output in response to a reception of the PWM drive signal during the data period.
  • the modulated light output represents the "0" data bit in response to the PWM drive signal including the "0” bit waveform.
  • the modulated light output represents the "1" data bit in response to the PWM drive signal including the "1” bit waveform.
  • ballast 110 Upon completion of stage 930, ballast 110 returns to stage 910 to await a new data period.

Landscapes

  • Circuit Arrangement For Electric Light Sources In General (AREA)
  • Optical Communication System (AREA)
  • Discharge-Lamp Control Circuits And Pulse- Feed Circuits (AREA)
  • Circuit Arrangements For Discharge Lamps (AREA)

Abstract

L'invention concerne un procédé pour activer une source lumineuse (100) comportant un ballast (110) en communication électrique avec une lampe (120). Ce procédé consiste à activer le ballast (110) en vue de déterminer (920) la puissance moyenne à appliquer à la lampe (120) pendant une période de transmission de données. Le procédé consiste également à activer le ballast (110) en vue de générer et de communiquer (930) à la lampe (120) pendant ladite période un signal d'excitation modulé en largeur d'impulsion. Le procédé consiste en outre à activer la lampe (120) en vue d'émettre (940) une puissance lumineuse modulée suite à la réception dudit signal d'excitation durant ladite période .
EP04735929.4A 2003-06-10 2004-06-03 Modulation de la puissance lumineuse pour la transmission de données Expired - Lifetime EP1637015B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US47722103P 2003-06-10 2003-06-10
PCT/IB2004/001842 WO2004110109A1 (fr) 2003-06-10 2004-06-03 Modulation de la puissance lumineuse pour la transmission de donnees

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Publication Number Publication Date
EP1637015A1 true EP1637015A1 (fr) 2006-03-22
EP1637015B1 EP1637015B1 (fr) 2014-12-03

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US (1) US7456589B2 (fr)
EP (1) EP1637015B1 (fr)
JP (1) JP2006527558A (fr)
CN (1) CN1802880B (fr)
WO (1) WO2004110109A1 (fr)

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US20070057639A1 (en) 2007-03-15
CN1802880B (zh) 2011-07-06
US7456589B2 (en) 2008-11-25
JP2006527558A (ja) 2006-11-30
CN1802880A (zh) 2006-07-12
WO2004110109A1 (fr) 2004-12-16
EP1637015B1 (fr) 2014-12-03

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